JPH04233191A - Dc arc furnace - Google Patents

Abstract

PURPOSE: To ensure the required deflection and/or symmetry of an arc by a method wherein the conductivity of a wated lining body in one section having a specific arrangement is larger than that of a given material in the other section by a predetermined value. CONSTITUTION: A sector 21 having an open angle of 45 to 90 deg. is symmetrically disposed toward a current feeding device 19. A carbon content of bricks 8a,..., 8c used as a current conductor of a coated lining body is slightly smaller than that of bricks in the other sector 22. Then the bricks of the sector 22 have a carbon content of 10 to 20wt.%, and hence the conductivity of the sector 22 is smaller that that of the sector 21. As a result, arc currents flowing through an electrode and a high current conductor 18 are distributed in such a manner that a higher current is passed through a fused material in the region of the sector 22 to compensate for the action of a deflection direct current magnetic field generated from the conductor 18, and consequently, the unnecessary deflection of an arc can be prevented.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a furnace vessel surrounded by a metal shell and at least one
one electrode and at least one bottom contact, in which the bottom of the furnace consists of a single-layer or multi-layer cover lining body, the cover lining body having conductive bricks or other equivalent inserts. The coated lining body rests on and abuts a contact plate covering a large portion of the bottom, the contact plate forming a bottom contact configured as an anode, and having a plurality of connection attachments. The present invention relates to a device having a mounting member extending through an opening in the bottom plate and connected via an electrical line to a current supply device located beside the furnace vessel.

[0002]The present invention is disclosed in US Pat. No. 4,550,413, for example.
This invention relates to the prior art as shown in the specification of the present invention.

0003

TECHNICAL BACKGROUND In high-power DC arc furnaces, the current flowing in the current supply lines and the take-off (output) lines causes a deflection of the arc. Arcing does not occur vertically. Rather, the arc is directed at the furnace wall, causing overheating there.

A "centering" of the arc can be effected by a special guiding arrangement of the current supply and take-off lines below and beside the furnace vessel. Therefore, US-A-455041
3 (US Pat. No. 4,550,413) and US-A-45
No. 77326 (U.S. Pat. No. 4,577,326) proposes to lay the line in such a way that the magnetic field induced by the passing direct current acts symmetrically on the arc. Proposed. These measures are expensive and, in addition to cost, increase the space requirements of the furnace. According to another measure, it is possible to compensate for asymmetries in the current supply and extraction lines by making the electrodes together with the electrode holder horizontally movable relative to the furnace vessel. This measure is also very expensive, since a corresponding space must be provided in the cover for the displacement of the electrode.

[0005] Although undesired deflections of the arc are caused by the current feed leads, in reality the arc is deflected in one direction or the other in a desired manner, for example in the region of an eccentric bottom spout, or In the case of continuously charged furnaces, it is often the case that even more heat has to be introduced in this region. This is only possible by horizontally moving movement of the electrode relative to the furnace vessel, which is very expensive.

[0006]

OBJECTS OF THE INVENTION The object of the invention is to provide a direct current arc furnace in which the desired deflection and/or symmetrization of the arc can be effected by simple means.

[0007]

[Structure of the Invention] According to the present invention, in order to solve the above problems,
For the intended deflection of the arc, one or more sections of the covering lining body consist of a material that has a lower electrical conductivity than the remaining sections.

[0008] Advantageously, the covering lining body, in the section facing the current supply device, at least partially consists of a given material, which has a lower electrical conductivity than in its remaining sections. It is possible to do so.

In the case of arc furnaces with an eccentric bottom outlet, the covering lining body in the area of the bottom outlet can have a lesser electrical conductivity than in the remaining areas, thus reducing the disadvantages of arcing. large deflections are avoided and thus more heat can be introduced into the melt.

In the case of electric arc furnaces for continuous charging of sponge iron or scrap iron, the desired deflection of the arc can be produced as follows: In electric arc furnaces, the coated lining has a lower electrical conductivity in the charged area than in the remaining areas. Thereby, the arc is directed (deflected in a desired manner) towards the charge melt, analogous to the case described above.
, thereby an improved and enhanced heat supply can be achieved.

A particular advantage of the present invention is that the desired deflection of the arc can be achieved without the need for expensive conductor runs beneath or beside the furnace vessel or expensive electrode placement techniques. Depending on the deflection, symmetrization can be carried out as necessary, or consciously,
It is possible to deflect the arc in a predetermined direction. Since the coated lining body must be replaced at regular intervals in any case, it is also advantageous to equip existing electric arc furnaces with the coated lining body of the invention.

Embodiments of the invention and the advantages obtained thereby will be explained with the aid of the figures.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The DC arc furnace of FIG. 1a has a furnace vessel 1 which has a shell 2 made of metal. Hearth lid (
cover) and electrode holder are peeled off. In the exemplary embodiment, the furnace has only one solid electrode 3 connected as a cathode, but the number of electrodes can also be two, three or more. Below the electrode 3, an electrode spot, ie a slag-free surface of the melt 4, is obtained in the usual manner. The furnace has a tapping device in the form of an eccentric spout 5 in the overhanging projection 6 of the furnace vessel. A bottom contact is attached to the bottom of the furnace. The bottom contact consists in the example of three coated lining bodies 7a to 7c of graphite or graphite-containing bricks 8a to 8c, which rest on a carrot-shaped contact plate 9. The connection (continuous)-attachment member 10 (FIG. 1-b) in the contact plate 9 projects downwardly to the outside through an opening 11 in the container bottom 12.

The bottom cover lining body is followed outwardly by a conventional furnace brickwork 13. The furnace vessel 12 is equipped with a cooling device (
(not shown). The bricks 8a to 8c of the covering lining bodies 7a to 7c serve as current conductors between the melt 14 and the contact plate 9.

Up to this point, DC arc furnaces correspond to the prior art, for example as described in US Pat. No. 4,228,314, German Patent No. 3022566, GB-A
2133125 (UK Patent Specification No. 2133125)
, DE-A3241978 (German Patent Publication No. 3241
No. 978). The first publication concerned with conventional electric arc furnaces and the last publication concerned with electric arc furnaces having an eccentric bottom outlet.

The outer shell 2 of the furnace vessel is tapered inward to form an inwardly projecting collar 15, the end 16 of which is bent upward. ing. The bottom plate 12 has a collar 15 extending in the radial direction. In the overlap region a ring 17 of insulating material is provided. The entire bottom area of the furnace is thus supported on the collar 15. The bottom region of the furnace is virtually floating within the furnace vessel. At the same time, an electrical insulation between the furnace shell 2 and the bottom plate 12 and thus also the bottom contact can be provided via the insulation material.

The condition of the distribution device of the connection fitting 9 is clear from the top view of the underside of the furnace vessel in FIG. Four mounting members 10 are shown regularly distributed over the bottom and a high current conductor 18 to a current supply 19 of the arc furnace. Opening angle typically 45° to 90° 45° to 9
The first sector 21 with 0° (this is the current feeder 19
The bricks 8a, 8b and/or 8c of the cover lining body 7a, 7b or 7c are made of a material with a lower carbon content than the bricks of the second sector 22.

The bricks of the second sector 22 are typically 1
It has a carbon content of 0-20% by weight. Therefore, the conductivity in the first sector 21 is lower than that outside the area. Without the conductor guiding arrangement as shown in FIG. Under the action of the current flowing through it, it will be deflected away from the current supply device 19. On the contrary, according to the composite coated lining body according to the invention:
The electrical/magnetic center of the bottom contact, considered in itself, is sham-shifted off the geometric center. In that way, the current distribution in the melt is influenced in the following way: more current flows into the melt in the region of the second sector 22 and thus the high current conductor 18
The deflection direct current fields (magnetic fields) due to this are influenced in such a way that they overlap with a compensating effect. As a result, arc operation without undesirable deflections is possible.

Both "normally conductive" and "relatively low conductive" bricks are completely commensurate with the state of the art and are provided by the associated companies in completely different specifications. In addition, bricks having a conductor different from graphite can also be used. For example, it is also possible to use bricks whose electrical conductivity is determined by the boride content. Furthermore, it is also possible to use bricks consisting of a substantially non-conductive core covered in whole or in part by a metal overlay.

Sectors 21, 22 with different conductivities
Alternatively, the above-mentioned covering lining body can also be constructed differently in terms of its electrical conductivity. For example, it is also possible to have the following configuration, that is, the current feeding device 12
It can also be provided that bricks of relatively low electrical conductivity or non-conductivity are mixed into the covering lining body in the section of the covering lining body facing towards.

[0021] It can be considered a disadvantage that the proposed approach under the new arrangement does not completely eliminate undesired deflections. For example, this may be because the opening angle α has been chosen too small or too large, or because the covering lining body in the first sector 21 has been designed incorrectly. Since the covering lining body must be replaced regularly in any case, the test phase is relatively short compared to the useful life of the furnace and therefore has little impact on the furnace operation and its economic efficiency.

In the case of arc furnaces with eccentric bottom sprue or in the case of arc furnaces in which scrap iron or sponge iron is continuously charged, in the region of the bottom sprue or charge:
The temperature in the melt is lower than in the remaining areas of the melt. By selecting differently conductive sections of the covering lining body, a desired deflection of the arc can be effected around such defined areas of the melt, even for such special purposes.

According to FIG. 4, a second sector 23 having bricks with low conductivity is provided beside the sector 21, and this second sector opens symmetrically toward the bottom hot water outlet 5 with an opening angle β. ing. The same considerations as mentioned above regarding symmetrization apply to the selection design of the opening angle and the conductivity of the brick. The configuration of the sector 23 alone allows the desired deflection to be applied also in the following cases: U.S. Pat. No. 4,577,326 U.S. Pat.
It can also be applied when using guided laying of lines (conductors) according to the prior art according to document No. 3.

FIG. 3 shows another method (third method) for exerting a control effect on the arc. This method holds true for arc furnaces with continuous charging with sponge iron pellets or scrap iron. In the case of a charge towards the feeder 19 (this is indicated by the arrow 24), the deflection in the direction of the charge is achieved in the following way: a sector with an opening angle ψ This causes the material of the covering lining body to have a lower electrical conductivity in the sectors 22 at 25 . In this case as well, it can be concluded that the means alone can be applied.

[0025]

Effects of the Invention According to the present invention, it is possible to realize a DC arc furnace in which the desired deflection and/or symmetry of the arc can be achieved by simple means, and it is possible to realize a direct current arc furnace in which the desired deflection and/or symmetry of the arc can be achieved, and it is possible to realize a direct current arc furnace in which an expensive conductor is laid under or beside the furnace vessel. This has the advantage that the arc can be deflected in a desired manner without having to do anything or use expensive arrangement techniques.

[Brief explanation of the drawing]

1 shows an embodiment of a DC arc furnace with an eccentric spout in longitudinal section, showing the electrical connections at the bottom of the furnace; FIG.

FIG. 2 is a plan view of the bottom of the arc furnace in FIG. 1;

FIG. 3 is a plan view of the jacket lining body of a direct current arc furnace with additional means for increasing the heat supply in the area of the bottom sprue;

4 shows a plan view of the jacket lining of the DC arc furnace of FIG. 1 with additional means for increasing the heat supply in the charging region; FIG.

[Explanation of symbols]

1 Furnace vessel 2. Outer jacket 3 Electrode 4 Melt 5 Eccentric hot water outlet 6 Overhanging protrusion

Claims (8)

[Claims] 1. A furnace vessel (1) surrounded by a metal outer shell (2) and at least one cathode configured as a cathode.
one electrode (3) and at least one bottom contact, in which the bottom of the furnace consists of a single-layer or multi-layer cover lining body (7a, 7b, 7c), which cover lining body is made of electrically conductive bricks ( 8a, 8b, 8c) or other equivalently functional inserts, and said covering lining body has a contact plate (P
) is placed and abutted on the contact plate (
P) constitutes a bottom contact configured as an anode and has a plurality of connecting fittings (10) passing through openings (11) in the bottom plate (12). , which is also connected via an electric line (18) to a current supply device (18) located beside the furnace vessel, in which the sheathing lining bodies (7a, 7b) are connected for the desired deflection of the arc. , 7c) consists of a material having a lower electrical conductivity than in the remaining sections (22). 2. The coated lining body (7a, 7b,
7c) consists at least partially of a given material in the section (21) facing the current feeder (19);
2. A DC arc furnace as claimed in claim 1, wherein said predetermined material has less electrical conductivity than in remaining sections thereof. 3. The coated lining body (7a, 7b,
7c) consists of a given material with a first sector (21) open towards the current feeder (19), which material has a lower electrical conductivity than in its second sector (22). The DC arc furnace according to claim 2, wherein the DC arc furnace has: 4. The opening angle of the first section (21) (
4. A DC arc furnace according to claim 3, wherein α) is between 20[deg.] and 180[deg.], for example between 45[deg.] and 90[deg.]. Claim 5: The first section or sector (2
The electrical conductivity of the covering lining body in 1) is at least 25% higher than in other sections or sectors (22).
5. The direct current arc furnace according to any one of claims 2 to 4, wherein the DC arc furnace is % small. 6. The DC arc as claimed in claim 1, having an eccentric bottom outlet (5) and in which the covering lining body in the area of the bottom outlet (5) has a lower electrical conductivity than in the remaining area. Furnace. 7. In an arc furnace for continuous charging of sponge iron or scrap iron, the coated lining body has a lower electrical conductivity in the area where the charging takes place than in the remaining areas. DC arc furnace. 8. The coated lining body consists of one or more layers of bricks (8a to 8c) which contain metals, graphite or borides as electrical conductors, or which are at least partially metal coated. The DC arc furnace according to any one of claims 1 to 7, wherein the DC arc furnace is made of bricks coated with.